Another instance of PHP 8.1 warning

 PHP Deprecated:  strlen(): Passing null to parameter #1 ($string) of type string is deprecated in /customfield/classes/handler.php on line 653

In our case the custom fields were generated programmatically and the 'description' field was null. Normally it would be filled from the field in the form and would be an empty string. So I guess it does not happen often but still possible.